1 /* Layout and location of TZif files. */ 2 3 #ifndef TZFILE_H 4 #define TZFILE_H 5 6 7 /* 8 ** This file is in the public domain, so clarified as of 9 ** 1996-06-05 by Arthur David Olson. 10 ** 11 ** $FreeBSD$ 12 */ 13 14 /* 15 ** This header is for use ONLY with the time conversion code. 16 ** There is no guarantee that it will remain unchanged, 17 ** or that it will remain at all. 18 ** Do NOT copy it to any system include directory. 19 ** Thank you! 20 */ 21 22 /* 23 ** Information about time zone files. 24 */ 25 26 #ifndef TZDEFRULES 27 # define TZDEFRULES "posixrules" 28 #endif /* !defined TZDEFRULES */ 29 30 31 /* See Internet RFC 8536 for more details about the following format. */ 32 33 /* 34 ** Each file begins with. . . 35 */ 36 37 #define TZ_MAGIC "TZif" 38 39 struct tzhead { 40 char tzh_magic[4]; /* TZ_MAGIC */ 41 char tzh_version[1]; /* '\0' or '2'-'4' as of 2021 */ 42 char tzh_reserved[15]; /* reserved; must be zero */ 43 char tzh_ttisutcnt[4]; /* coded number of trans. time flags */ 44 char tzh_ttisstdcnt[4]; /* coded number of trans. time flags */ 45 char tzh_leapcnt[4]; /* coded number of leap seconds */ 46 char tzh_timecnt[4]; /* coded number of transition times */ 47 char tzh_typecnt[4]; /* coded number of local time types */ 48 char tzh_charcnt[4]; /* coded number of abbr. chars */ 49 }; 50 51 /* 52 ** . . .followed by. . . 53 ** 54 ** tzh_timecnt (char [4])s coded transition times a la time(2) 55 ** tzh_timecnt (unsigned char)s types of local time starting at above 56 ** tzh_typecnt repetitions of 57 ** one (char [4]) coded UT offset in seconds 58 ** one (unsigned char) used to set tm_isdst 59 ** one (unsigned char) that's an abbreviation list index 60 ** tzh_charcnt (char)s '\0'-terminated zone abbreviations 61 ** tzh_leapcnt repetitions of 62 ** one (char [4]) coded leap second transition times 63 ** one (char [4]) total correction after above 64 ** tzh_ttisstdcnt (char)s indexed by type; if 1, transition 65 ** time is standard time, if 0, 66 ** transition time is local (wall clock) 67 ** time; if absent, transition times are 68 ** assumed to be local time 69 ** tzh_ttisutcnt (char)s indexed by type; if 1, transition 70 ** time is UT, if 0, transition time is 71 ** local time; if absent, transition 72 ** times are assumed to be local time. 73 ** When this is 1, the corresponding 74 ** std/wall indicator must also be 1. 75 */ 76 77 /* 78 ** If tzh_version is '2' or greater, the above is followed by a second instance 79 ** of tzhead and a second instance of the data in which each coded transition 80 ** time uses 8 rather than 4 chars, 81 ** then a POSIX-TZ-environment-variable-style string for use in handling 82 ** instants after the last transition time stored in the file 83 ** (with nothing between the newlines if there is no POSIX.1-2017 84 ** representation for such instants). 85 ** 86 ** If tz_version is '3' or greater, the above is extended as follows. 87 ** First, the TZ string's hour offset may range from -167 88 ** through 167 as compared to the POSIX-required 0 through 24. 89 ** Second, its DST start time may be January 1 at 00:00 and its stop 90 ** time December 31 at 24:00 plus the difference between DST and 91 ** standard time, indicating DST all year. 92 */ 93 94 /* 95 ** In the current implementation, "tzset()" refuses to deal with files that 96 ** exceed any of the limits below. 97 */ 98 99 #ifndef TZ_MAX_TIMES 100 /* This must be at least 242 for Europe/London with 'zic -b fat'. */ 101 # define TZ_MAX_TIMES 2000 102 #endif /* !defined TZ_MAX_TIMES */ 103 104 #ifndef TZ_MAX_TYPES 105 /* This must be at least 18 for Europe/Vilnius with 'zic -b fat'. */ 106 # define TZ_MAX_TYPES 256 /* Limited by what (unsigned char)'s can hold */ 107 #endif /* !defined TZ_MAX_TYPES */ 108 109 #ifndef TZ_MAX_CHARS 110 /* This must be at least 40 for America/Anchorage. */ 111 # define TZ_MAX_CHARS 50 /* Maximum number of abbreviation characters */ 112 /* (limited by what unsigned chars can hold) */ 113 #endif /* !defined TZ_MAX_CHARS */ 114 115 #ifndef TZ_MAX_LEAPS 116 /* This must be at least 27 for leap seconds from 1972 through mid-2023. 117 There's a plan to discontinue leap seconds by 2035. */ 118 # define TZ_MAX_LEAPS 50 /* Maximum number of leap second corrections */ 119 #endif /* !defined TZ_MAX_LEAPS */ 120 121 #endif /* !defined TZFILE_H */ 122